Hormones

Hormones are the body's own messenger substances which carry out specific regulating functions in the cells of their respective effector organs and thereby control physiologic processes. Their regulation takes place on three levels: the hypothalamic level (primary releasing function), the stimulator level in the pituitary gland, and the glandular level in the respective organs. The secretion of the hormones is controlled via feedback mechanisms among the three levels or via the blood levels of the substance they are regulating (e.g. insulin and glucose, glucagon and glucose, calcium and parathyroid hormone). When the mother is treated with hormones, there may also be effects on the fetus at the various levels of these regulatory mechanisms. Drugs affecting maternal endocrine system might also affect the fetal system. Maternal endocrine diseases (i.e. diabetes, hyper or hypothyroidism) might have negative effects on the embryo and fetus often not related to the fetal hormones (i.e. diabetic embryopathy and fetopathy). The classical hormones, antihormones and maternal disease of the endocrine system discussed in this chapter are distinguished from local tissue factors or mediators, which also include, among other substances, the prostaglandins and leukotrienes.